Are Cenozoic relict species also climatic relicts? Insights from the macroecological evolution of the giant sedges of Carex sect. Rhynchocystis.

PREMISE Most of the Paleotropical flora widely distributed in the Western Palearctic became extinct during the Mio-Pliocene as a result of global geoclimatic changes. A few elements from this Cenozoic flora are believed to remain as relicts in Macaronesia, forming part of the Macaronesian Laurel Forest. Although the origins of the present species assembly are known to be heterogeneous, it is unclear whether some species should be considered climatic relicts with conserved niches. An ideal group to study such relict characteristics is the Miocene lineage of Carex sect. Rhynchocystis, which comprises four species distributed in the mainland Palearctic and Macaronesia. METHODS We reconstructed the current and past environmental spaces for extant mainland and Macaronesian species, and for the occurrence of Pliocene fossils. We also studied the bioclimatic niche evolution. Species Distribution Modeling and Ensemble Small Modeling were performed to assess the potential distribution over time. KEY RESULTS The ecological requirements of Macaronesian species did not overlap with those of either mainland species or with the Pliocene fossils. Conversely, the niches of mainland species displayed significant similarity and equivalence. The ecological differentiation within Macaronesia and similarity across the continent were evaluated in bioclimatic evolution and distribution modeling analyses. CONCLUSIONS Macaronesian species are not climatic relicts from the Paleotropical flora, but instead seems have changed the ecological niche from their ancestors. By contrast, despite their ancient divergence (Late Miocene), mainland C. pendula and C. agastachys show conserved niches, with competitive exclusion likely shaping their mostly allopatric ranges. This article is protected by copyright. All rights reserved.